This invention relates to integrated circuit metallization patterning in general, and in particular to laser patterning of integrated circuit metallization.
The use of thin film metallization in the fabrication of integrated circuits is well known. The patterning of the metallization is also well known, and both are typical integrated circuit fabrication processes. An example of this use is disclosed by Darley et al in U.S. Pat. No. 4,202,003, which is hereby incorporated by reference.
The use of lasers in patterning of metallization is a relatively recent development. Schulte et al, in U.S. patent application Ser. No. 189,495 discloses the use of laser to sublimate metal from areas where the material underneath the metal had very low heat transfer capability. After sublimation, metal vapor is moved away by convection.
The removal of the metal vapor by convection has some problems. For one, some of the metal is redeposited back on the surface. Also, in cases where recovery of the removed metal is desirable, that task is difficult. Another consideration is that unconfined vaporized metal tends to condense on the final laser optics, resulting in damage to them.
Other vapor collection schemes have been considered, such as gas jets, vacuum collectors, and electrostatic collectors, but were found to be unsuccessful, inefficient, impractical, or expensive and difficult to implement.
It is therefore an object of this invention to provide a method for confining vaporized metal after sublimation of the metal by laser energy. It is a further object of this invention to provide a means for a simple reclamation process allowing almost 100% recovery of removed metal.